How do you get the World Champion Minions Icon?
It was an esports viewing reward. Riot's description in the client reads: “Unlocked by watching games during the 2018 Worlds event.”
Is the World Champion Minions Icon still available?
No. The World Champion Minions Icon was an esports viewing reward: it dropped to viewers who watched LoL Esports broadcasts or completed LoL Esports missions in 2018. Past drops are not handed out again, so it cannot be earned anymore.
